Development of group III-V flexible solar cells on patterned Si substrates

In this study, a wide bandgap GaInP ternary semiconductor compound was grown on Si substrates by molecular beam epitaxy instead of lattice-matched GaAs substrates. Then the grown GaInP thin films were transferred to flexible carriers. Finally, solar cell devices were fabricated. To suppress crystal defects due to lattice mismatch, ordered and disordered patterning was applied to the Si substrates prior to growth. The Si substrates were patterned by two different methods: ordered patterning using nanosphere lithography and disordered patterning using AgNO3 with metal-assisted chemical etching. Cross-sectional scanning electron microscopy images of the buffer GaAs layer grown on the patterned substrates showed that the dislocations were significantly reduced compared to the growth on the bare Si substrate. The GaInP thin films were transferred to a flexible carrier by epitaxial lift-off method. Single junction GaInP solar cell devices characterized by electro-optic methods. The FWHM of the GaAs buffer layer and GaInP thin films grown on patterned Si substrates were obtained as ~180 and ~350 arcsec, respectively. The electrical conversion efficiencies of ordered and disordered patterned single junction GaInP solar cell devices were obtained as 0.25 and 0.39%, respectively. Also, 1.03% electrical conversion efficiency was obtained from single junction GaInP solar cells grown on 4o miscut Si substrate. As for reference, 7.04% electrical conversion efficiency was obtained from single junction GaInP solar cells grown on GaAs substrate.